1. Field of the Invention
Aspects of the present invention relate to an electron emission device, and more particularly, to an electron emission device having a focusing electrode that is improved to enhance the focusing efficiency of an electron beam, and an electron emission display using the electron emission device.
2. Description of the Related Art
Generally, electron emission elements are classified into those using a hot cathode as an electron emission source, and those using a cold cathode as the electron emission source. There are several types of cold cathode electron emission elements, including Field Emitter Array (FEA) elements, Surface Conduction Emitter (SCE) elements, Metal-Insulator-Metal (MIM) elements, and Metal-Insulator-Semiconductor (MIS) elements.
The FEA element includes an electron emission region and cathode and gate electrodes that are driving electrodes for controlling the electron emission from the electron emission region. The electron emission regions are formed of a material having a relatively low work function or a relatively large aspect ratio, such as a carbon-based material or a nanometer-sized material so that electrons can be effectively emitted when an electric field is applied thereto under a vacuum atmosphere.
The electron emission elements are arrayed on a first substrate to form an electron emission device. To form an electron emission display, the electron emission device is combined with a second substrate, on which a light emission unit having phosphor layers and an anode electrode is formed.
In the electron emission display, there has been an endeavor to improve the display quality by inducing an electron beam path in a target direction. For example, when the electrons emitted from the electron emission region are diffused and travel toward the second substrate, they land on a black layer adjacent to a target phosphor layer of a corresponding pixel and other phosphor layers as well as on the target phosphor layer, thereby emitting undesired color light. Therefore, a focusing electrode for controlling the electron beam has been proposed. The focusing electrode is generally disposed on an uppermost layer of the electron emission device and provided with openings through which respective electron beams pass. The electrons passing through each opening are converged toward a central axis of the electron beam.
However, since the focusing electrode is formed in a single body and the electron beams are converged by a single focusing voltage, it is difficult to precisely control a shape of an electron beam spot. That is, it is impossible to control the shape of the electron beam spot reaching each phosphor layer in horizontal and vertical directions of a screen and the electron beam convergent efficiency is low.